Field of the Invention
The present invention relates to a direct current fan, and in particular relates to a direct current fan that can be directly driven by high direct current voltage.
Description of the Related Art
The operation voltage of the electrical fan is typically not high, and the most commonly used operation voltage may be 5V, 12V, 24V or 48V. However, the commercial power system provides an alternating current (AC) voltage and the magnitude of the AC voltage is between 110V and 220V, wherein a power supply is required to transform the AC voltage into a low DC voltage. Please refer to FIG. 1, wherein FIG. 1 is a schematic diagram of a conventional DC fan and a power supply. The power supply 11 receives the AC voltage Vac and outputs a second DC voltage VdcL to drive the DC fan 12. The power supply 11 comprises an EMI (Electromagnetic Interference) filter 13, a PFC (power factor correction stage) stage 14, and a DC/DC converter 14. The EMI filter 13 filters out noises of the input AC voltage. The PFC stage 14 transforms the filtered AC voltage into a first DC voltage VdcH. The DC/DC converter 15 converts the first DC voltage VdcH to the second DC voltage VdcL, wherein the magnitude of the second DC voltage VdcL is smaller than the magnitude of the first DC voltage VdcH.
However, due to the design limitation of the conventional DC fan, the conventional DC fan may operate at a high current and low voltage level, which easily causes transmission loss. Also, under this circumstance, when the power supply executes the voltage transformation operation, it may also cause a power loss. Thus, the control mechanism of the conventional DC fan easily causes undesired waste of resources?.